The Nobel-Winning Material at the Heart of Samsung QLEDs [Interview on Real Quantum Dots Part 1.]

[Samsung Newsroom]

“One of the reasons Samsung focused on quantum dots is their exceptionally narrow peaks of the emission spectrum.”

— Sanghyun Sohn, Samsung Electronics

 

In 2023, the Nobel Prize in Chemistry was awarded for the discovery and synthesis of quantum dots. The Nobel Committee recognized the groundbreaking achievements of scientists in the field — noting that quantum dots have already made significant contributions to the display and medical industries, with broader applications expected in electronics, quantum communications and solar cells.

 

Quantum dots — ultra-fine semiconductor particles — emit different colors of light depending on their size, producing exceptionally pure and vivid hues. Samsung Electronics, the world’s leading TV manufacturer, has embraced this cutting-edge material to enhance display performance.

 

Samsung Newsroom sat down with Taeghwan Hyeon, a distinguished professor in the Department of Chemical and Biological Engineering at Seoul National University (SNU); Doh Chang Lee, a professor in the Department of Chemical and Biomolecular Engineering at the Korea Advanced Institute of Science and Technology (KAIST); and Sanghyun Sohn, Head of Advanced Display Lab, Visual Display (VD) Business at Samsung Electronics, to explore how quantum dots are ushering in a new era of display technology.

 

• • Understanding the Band Gap
  • Quantum Dots – The Smaller the Particle, the Larger the Band Gap
  • Engineering Behind Quantum Dot Films
  • Real QLED TVs Use Quantum Dots To Create Color

 

 

 

Understanding the Band Gap

 

“To understand quantum dots, one must first grasp the concept of the band gap.”

— Taeghwan Hyeon, Seoul National University

 

The movement of electrons causes electricity. Typically, the outermost electrons — known as valence electrons — are involved in this movement. The energy range where these electrons exist is called the valence band, while a higher, unoccupied energy range that can accept electrons is called the conduction band.

 

An electron can absorb energy to jump from the valence band to the conduction band. When the excited electron releases that energy, it falls back into the valence band. The energy difference between these two bands — the amount of energy an electron must gain or lose to move between them — is known as the band gap.

 

▲ A comparison of energy band structures in insulators, semiconductors and conductors

 

Insulators like rubber and glass have large band gaps, preventing electrons from moving freely between bands. In contrast, conductors like copper and silver have overlapping valence and conduction bands — allowing electrons to move freely for high electrical conductivity.

 

Semiconductors have a band gap that falls between those of insulators and conductors — limiting conductivity under normal conditions but allowing electrical conduction or light emission when electrons are stimulated by heat, light or electricity.

 

“To understand quantum dots, one must first grasp the concept of the band gap,” said Hyeon, emphasizing that a material’s energy band structure is crucial in determining its electrical properties.

 

 

Quantum Dots – The Smaller the Particle, the Larger the Band Gap

 

“As quantum dot particles become smaller, the wavelength of emitted light shifts from red to blue.”

— Doh Chang Lee, Korea Advanced Institute of Science and Technology

 

Quantum dots are nanoscale semiconductor crystals with unique electrical and optical properties. Measured in nanometers (nm) — or one-billionth of a meter — these particles are just a few thousandths the thickness of a human hair. When a semiconductor is reduced to the nanometer scale, its properties change significantly compared to its bulk state.

 

In bulk states, particles are sufficiently large so the electrons in the semiconductor material can move freely without being constrained by their own wavelength. This allows energy levels — the states that particles occupy when absorbing or releasing energy — to form a continuous spectrum, like a long slide with a gentle slope. In quantum dots, electron movement is restricted because the particle size is smaller than the electron’s wavelength.

 

▲ Size determines the band gap in quantum dots

 

Imagine scooping water (energy) from a large pot (bulk state) with a ladle (bandwidth corresponding to an electron’s wavelength). Using the ladle, one can adjust the amount of water in the pot freely from full to empty — this is the equivalent of continuous energy levels. However, when the pot shrinks to the size of a teacup — like a quantum dot — the ladle no longer fits. At that point, the cup can only be either full or empty. This illustrates the concept of quantized energy levels.

 

“When semiconductor particles are reduced to the nanometer scale, their energy levels become quantized — they can only exist in discontinuous steps,” said Hyeon. “This effect is called ‘quantum confinement.’ And at this scale, the band gap can be controlled by adjusting particle size.”

 

The number of molecules within the particle decreases as the size of the quantum dot decreases, resulting in weaker interactions of molecular orbitals. This strengthens the quantum confinement effect and increases the band gap.¹ Because the band gap corresponds to the energy released through relaxation of an electron from the conduction band to the valence band, the color of the emitted light changes accordingly.

 

“As particles become smaller, the wavelength of emitted light shifts from red to blue,” said Lee. “In other words, the size of the quantum dot nanocrystal determines its color.”

 

 

Engineering Behind Quantum Dot Films

 

“Quantum dot film is at the core of QLED TVs — a testament to Samsung’s deep technical expertise.”

— Doh Chang Lee, Korea Advanced Institute of Science and Technology

 

Quantum dots have attracted attention across a variety of fields, including solar cells, photocatalysis, medicine and quantum computing. However, the display industry was the first to successfully commercialize the technology.

 

“One of the reasons Samsung focused on quantum dots is the exceptionally narrow peaks of their emission spectrum,” said Sohn. “Their narrow bandwidth and strong fluorescence make them ideal for accurately reproducing a wide spectrum of colors.”

 

▲ Quantum dots create ultra-pure red, green and blue (RGB) colors by controlling light at the nanoscale, producing narrow bandwidth and strong fluorescence.

 

To leverage quantum dots effectively in display technology, materials and structures must maintain high performance over time, under harsh conditions. Samsung QLED achieves this through the use of a quantum dot film.

 

“Accurate color reproduction in a display depends on how well the film utilizes the optical properties of quantum dots,” said Lee. “A quantum dot film must meet several key requirements for commercial use, such as efficient light conversion and translucence.”

 

▲ Sanghyun Sohn

 

The quantum dot film used in Samsung QLED displays is produced by adding a quantum dot solution to a polymer base heated to a very high-temperature, spreading it into a thin layer and then curing it. While this may sound simple, the actual manufacturing process is highly complex.

 

“It’s like trying to evenly mix cinnamon powder into sticky honey without making lumps — not an easy task,” said Sohn. “To evenly disperse quantum dots throughout the film, several factors such as materials, design and processing conditions must be carefully considered.”

 

Despite these challenges, Samsung pushed the boundaries of the technology. To ensure long-term durability in its displays, the company developed proprietary polymer materials specifically optimized for quantum dots.

 

“We’ve built extensive expertise in quantum dot technology by developing barrier films that block moisture and polymer materials capable of evenly dispersing quantum dots,” he added. “Through this, we not only achieved mass production but also reduced costs.”

 

Thanks to this advanced process, Samsung’s quantum dot film delivers precise color expression and outstanding luminous efficiency — all backed by industry-leading durability.

 

“Brightness is typically measured in nits, with one nit equivalent to the brightness of a single candle,” explained Sohn. “While conventional LEDs offer around 500 nits, our quantum dot displays can reach 2,000 nits or more — the equivalent of 2,000 candles — achieving a new level of image quality.”

 

▲ RGB gamut comparisons between visible light spectrum, sRGB and DCI-P3 in a CIE 1931 color space

* CIE 1930: A widely used color system announced in 1931 by the Commission internationale de l’éclairage
* sRGB (standard RGB): A color space created cooperatively by Microsoft and HP in 1996 for monitors and printers
* DCI-P3 (Digital Cinema Initiatives – Protocol 3): A color space widely used for digital HDR content, defined by Digital Cinema Initiatives for digital projectors

 

By leveraging quantum dots, Samsung has significantly enhanced both brightness and color expression — delivering a visual experience unlike anything seen before. In fact, Samsung QLED TVs achieve a color reproduction rate exceeding 90% of the DCI-P3 (Digital Cinema Initiatives – Protocol 3) color space, the benchmark for color accuracy in digital cinema.

 

“Even if you have made quantum dots, you need to ensure long-term stability for them to be useful,” said Lee. “Samsung’s industry-leading indium phosphide (InP)-based quantum dot synthesis and film production technologies are testament to Samsung’s deep technical expertise.”

 

 

Real QLED TVs Use Quantum Dots To Create Color

 

“The legitimacy of a quantum dot TV lies in whether or not it leverages the quantum confinement effect.”

— Taeghwan Hyeon, Seoul National University

 

As interest in quantum dots grows across the industry, a variety of products have entered the market. Nonetheless, not all quantum dot-labeled TVs are equal — quantum dots must sufficiently contribute to actual image quality.

 

▲ Taeghwan Hyeon

 

“The legitimacy of a quantum dot TV lies in whether or not it leverages the quantum confinement effect,” said Hyeon. “The first, fundamental requirement is to use quantum dots to create color.”

 

“To be considered a true quantum dot TV, quantum dots must serve as either the core light-converting or primary light-emitting material,” said Lee. “For light-converting quantum dots, the display must contain an adequate amount of quantum dots to absorb and convert blue light emitted by the backlight unit.”

 

▲ Doh Chang Lee

 

“Quantum dot film must contain a sufficient amount of quantum dots to perform effectively,” repeated Sohn, emphasizing the importance of quantum dot content. “Samsung QLED uses more than 3,000 parts per million (ppm) of quantum dot materials. 100% of the red and green colors are made through quantum dots.”

 

 

Samsung began developing quantum dot technology in 2001 and, in 2015, introduced the world’s first no-cadmium quantum dot TV — the SUHD TV. In 2017, the company launched its premium QLED lineup, further solidifying its leadership in the quantum dot display industry.

 

In the second part of this interview series, Samsung Newsroom takes a closer look at how Samsung not only commercialized quantum dot display technology but also developed a cadmium-free quantum dot material — an innovation recognized by Nobel Prize-winning researchers in chemistry.

 

 

¹ When a semiconductor material is in its bulk state, the band gap remains fixed at a value characteristic of the material and does not depend on particle size.

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